varying vec4 diffuse, ambientGlobal, ambient;
varying vec3 normal, lightDir, halfVector;
varying float dist;


void main() {
	vec3 n, halfV, viewV, ldir;
	float NdotL, NdotHV;
	vec4 color = ambientGlobal;
	float att;
	
	/* a fragment shader can't write a varying variable, hence we need
	a new variable to store the normalized interpolated normal */
	n = normalize(normal);
	
	/* compute the dot product between normal and normalized lightdir */
	NdotL = max(dot(n, normalize(lightDir)), 0.0);

	if (NdotL > 0.0) {
		att = 1.0 / (gl_LightSource[0].constantAttenuation +
				gl_LightSource[0].linearAttenuation * dist +
				gl_LightSource[0].quadraticAttenuation * dist * dist);
		color += att * (diffuse * NdotL + ambient);
	
		
		halfV = normalize(halfVector);
		NdotHV = max(dot(n, halfV), 0.0);
		color += att * gl_FrontMaterial.specular * gl_LightSource[0].specular * 
						pow(NdotHV, gl_FrontMaterial.shininess);
	}

	gl_FragColor = color;
}
